ILYA SOMIN looks at a timely book from Sanford Levinson, Nullification and Secession in Modern Constitutional Thought. “While many people associate secessionism with the Confederacy and efforts to protect slavery, and nullification with state resistance to the civil rights movement, this book shows that both tactics were often advocated by political movements on both the right and the left. In the antebellum period for example, nullificationist tactics were adopted by both southerners seeking to protect slavery, and northerners trying to resist the federal Fugitive Slave Act. Like many political strategies, nullification and secession can be used to promote both good causes and evil ones.”